Kaiapoi man Brett Wentworth says his family will be forced to live in caravans for four months because the Canterbury Earthquake Recovery Authority (Cera) has refused to extend the final settlement date for their red-zoned house.

Wentworth said the family is desperate to move from the damaged, rundown property into their new home in Flaxton, but because of unexpected delays, their new home will not be ready until May or June.

''I just cannot see any reason why we can't stay.''

Cera chief Roger Sutton said homeowners would be given 14 day's grace, but would be charged penalty rates if they continued to occupy their house after that.

The news of the settlement date had come as a surprise to Wentworth, who said he did not realise it was final, as there had been many extensions before.

Sutton said the cost to the government and the Waimakariri District Council of maintaining the infrastructure in the red zone for a very small number of homes was not viable in the long term.

''The cost of keeping services running to homes is approximately $500 per week per occupied house, and at present the estimated upkeep will cost just under $1 million each month. That will reduce as homes are vacated.''

However, Wentworth said he did not believe allowing his family to stay for another few months would cost the government or the council anything.

He had been told by a policeman patrolling the red zone in Kaiapoi it was a good security measure to have people living there.

Wentworth said moving his family and transport business to the Flaxton section would be a costly and stressful exercise.

As there is no power or water at the site, he would need to borrow or hire two or three caravans, a generator, port-a-loo and port-a-shower. ''We don't want to be here, but I don't want to live up there in third world conditions,'' he said.

His argument is that he can't see why they can't stay in a perfectly good house in the red zone until their new house is finished.